For a long time foodstuffs, whether foodstuffs for human consumption or also animal feed products, have been preserved by being stored either in a can or in a glass jar closed with a lid. However, these packaging systems have some serious disadvantages, inter alia the high intrinsic weight, the energy-intensive production and the troublesome opening.
Alternative packaging systems for storing foodstuffs for a long period of time as far as possible without impairment are known from the prior art. These are containers produced from sheetlike composites—often also called laminate. Such sheetlike composites are often built up from a layer of thermoplastic, a carrier layer usually made of cardboard or paper, an adhesion promoter layer, an aluminium layer and a further layer of plastic. Such a sheetlike composite is disclosed, inter alia, in WO 90/09926. Such laminated containers already have many advantages over the conventional glass jars and cans, for example space-saving storage and low intrinsic weight. Nevertheless, possibilities for improvement also exist for these packaging systems.
Thus, in the production process, in particular during closing of the abovementioned containers, adhesion of the surface of the containers to be closed to the closing tools occurs again and again. Damage and defects in the packaging can consequently occur, as a result of which this is damaged visually, or damage occurs inside the sheetlike composite. This is particularly undesirable, since this step is at the end of the creation of value and higher costs are therefore caused by withdrawal of damaged packs and claims due to imperfect seals. Thus, for example, damage to the barrier layers or layers of plastic, delaminations or cracks in the carrier layer may occur.
The problems which arise during closing of the containers already filled with a foodstuff are, inter alia, the following: The containers of the abovementioned type are as a rule closed by softening, superficial melting or liquefying the layers of plastic of the container. These layers of plastic often have tacky properties in the softened, molten or liquid state, so that the container adheres to the closing tool in this tacky region. In addition to damage and defective packs, this also leads to expensive, shorter maintenance intervals for the closing tool. The abovementioned difficulties during closing could thus be avoided if the temperature at the closing point were to be kept lower. The tackiness of a substance in general decreases with decreasing temperature, which would lead to less adhesion of the containers to the closing tool. Nevertheless, closure points produced in this manner are often less tight, which in turn can lead to a reduced shelf life and reduced quality of the foodstuffs contained in the container.